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m_fixed.pas
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m_fixed.pas
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//------------------------------------------------------------------------------
//
// DoomXS - A basic Windows source port of Doom
// based on original Linux Doom as published by "id Software"
// Copyright (C) 1993-1996 by id Software, Inc.
// Copyright (C) 2021-2022 by Jim Valavanis
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
// 02111-1307, USA.
//
//------------------------------------------------------------------------------
// Site: https://sourceforge.net/projects/doomxs/
//------------------------------------------------------------------------------
unit m_fixed;
interface
const
FRACBITS = 16;
FRACUNIT = 1 shl FRACBITS;
type
fixed_t = integer;
Pfixed_t = ^fixed_t;
fixed_tArray = packed array[0..$FFFF] of fixed_t;
Pfixed_tArray = ^fixed_tArray;
function FixedMul(const a, b: fixed_t): fixed_t;
function FixedDiv(const a, b: fixed_t): fixed_t;
implementation
uses
d_delphi;
function FixedDiv2(const a, b: fixed_t): fixed_t; assembler;
asm
mov ebx, b
mov edx, eax
sal eax, 16
sar edx, 16
idiv ebx
end;
function FixedMul(const a, b: fixed_t): fixed_t; assembler;
asm
imul b
shrd eax, edx, 16
end;
function FixedDiv(const a, b: fixed_t): fixed_t;
begin
if _SHR(abs(a), 14) >= abs(b) then
begin
if a xor b < 0 then
Result := MININT
else
Result := MAXINT;
end
else
Result := FixedDiv2(a, b);
end;
end.